Method and apparatus for measuring porosity of solids



Aug. 24, 1943. w, HQRNER 2,327,642

METHOD AND APPARATUS FOR MEASURING POROSITY 0F SOLIDS Original Filed Jan. 3, 1938 INVENTOR William Lfiomer -of the sand by dividing the latter measurement by the measurement of the total volume.

may serve to prevent the sample from being a suitable air vent at its top and an inlet UNITED STATES PATENT: OFFICE cream, monmsirmamsmamsnamc ronosnrorsouns n h of .nll. il

thigh-1am January 3,1838,Sfliallo.

8,I$lll,$efiallio.35l,89l

rockorearthioemations. Th presentapplica- 5,

tion is a division of my applieafion ll33,lil8,filed.lanuary 3, 1938.

011s oi the quantitaiive measurements made Serial no.

'- mcore samples takenfiomsandsthronghwhich oflwells are drilled is that of Pamela, i. e. the

percentage of p ce of'the sample occppied by pores. 'Fnrthenporesoisnchacoresamplemay beiihedwithliquidorgaeorbomanditis desirableto new the pore space filledi y'gas fered with, and subsequently measurin the vol-' umeoftheporespaceoccupiedbythegas. In

. the present embodiment thislatter step is accomplished by forcing a non-compresible liquid in whichthesampleisimmersedintotheporesto compress and supplant the gas therein, and measuring the volume of the liquid required to supplant the gas. The reading thus obtained is then translated into percent gas per imit volume this method of analysing the free gas content or the amount of pore space of a porous body, it is desirable to use a liquid which does not chemically react with the materials comprising the sample and which has a surface tension such that the liquid does not penetrate the pores without being forced into them. Qne liquld that I have found which fulfills these requirements is Othcr liquids, however, may be u'sed,wh'ich have a surface tension such 'as to wet the sample being analysed, and when using such liquids, the sample may first be coated with collodion which wetted by the liquid but which does not prevent subsequent penetration of the liquid through the a In carrying out the method'a sample chamber iniishottomisshapedsofllatasannn-commssmle' liquid is flooded into the chamber throughthebottomallgasisdrivenoutoithe chamberaheadofthelimfidastheliquidreaches thevent. Theamountofliquidthusreqlflredto fillthe chamberissuitab ly measured andthe liqnidisthmatleastpartlaliywithdrawnirom thechamber.

A core sample is now suitably shaped 'ia'immedto eliminate piisandcavitiaon its suriacethatmightretainairbubhlaandreduced to a size receivable by the sample container. The

sample is thenplaced in the container. The liquidisagamiloodedintothechamberandthe l5amountoiliquidreqtdredtofillthechamber withthesampleis noted, thedifference between this reading and the former reading being a measurement of the volume of the sample. The mtisnowclosedandtheliquidissubjectedto a pressure of, for example, 50 atmospheres, which causes the liquid to penetrate the pores, comprwingandsupplantingthegaspresentsothat it occupies one-flflrieth of the volume that it normally would c py at atmospheric pressure. The 'volume of the liquid thus entering the pores of the sample is measured and may be corrected upwards by two percent to compensate for the residual volume of the gas at 50 atmospheres.

From this reading, and the former readin of the volume of the sample, is obtained the fraction of the core volume occupied by free gas.

Further, the rate at which the liquid enters the core pores under 50 atmospheres of pressure may be taken as an indication of the permeability of the core sample-i. e. the resistance of the sample to the flow of fluid through it.

Referring to Figure l, the apparatus is shown for carrying out the method described above. A sampling chamber generally indicated at III is connected through an inlet l2 with a plunger indicated at M of amercury pump. The chamber III is closed at its top by a suitable cover plate I G which may be boltedin place by bolts l8 after the sample is placed in the chamber.

45 The joint between cover and chamber is made fluid-tight by a. suitable gasket 20. The inside. of the cover is conically shaped, as shown, and provided with a small vent 22 at the apex of the cone. The small-outlet may be closed ofiby a needle valve 24 which is suitably threaded down through a support 26 to set in the opening 22.

With this construction the sample may be 'placedinthechamberwhilethechamberis empty by simply removing the cover l6 and then bolting the cover back on. It ispossible'to tell of a heavy base 39 and the guide rods.

when the chamber is full of mercury with no occluded air by filling the chamber with mercury until the mercury appears in the small vent 22.

The inlet I2 of the chamber 40 communicates with the plunger chamber in which a plunger 28. is reciprocally mounted, and passes out of the chamber through suitable bearing and stuffing box generally indicated at'32. The outer end of the plunger carries a slider 33 sliding along.

suitable guide rods 34. Further, the plunger is hollow and threaded to receive a plunger-operating screw 35'one end of which is suitably rotatably mounted in thrust bearings generally indicated at 36 mounted in a journal 31 secured with respect to the plunger chamber M by means Keyed to the operating screw 35 is a hand-wheel 38 used for operating the screw.

The top guide rod 366 is suitably marked off in units of measurement such, for example, as

cubic centimeters, and the hub of the handwheel is also suitably marked in cubic centimeters, but in thousandths of cubic centimeters and in accordance with the pitch of the threads on the operating screw so that the position of the plunger may be read in terms of cubic centimeters and hundredths of cubiccentimeters from the scale on the guide rod and in thousandths of cubic centimeters from the scale on the hub 48.

The end of the plunger chamber opposite the :7

wheel until'mercury appear at the outlet 22,

and the position of the plunger is noted from the scale. 'The plunger is then retracted and the lid taken ofi and the sample, suitably prepared, is put into the chamber and the lid bolted back on. With the needle valve still open the plunger is again moved inwardly by the handwheel until the mercuryagain appears at the outlet 22 at which time the position of the plunger is again noted. From the difference of the two readings th volume of the sample is ob tained. The needle valve is now closed and the hand-wheel is operated to move the plunger inwardly to maintain a pressure on'the gauge equivalent to 50 atmospheres, the hand-wheel being moved as fast and for such length of time as is required to maintain this pressure. After it is no longer necessary to move the hand-wheel to keep the pressure at 50 atmospheres, the readings on thetwo scales are again noted and the difference between this reading and the last succeeding reading gives correctly the volume of mercury necessary to compress the gas-in the sample and to fill the pore space occupied by the gas. This latter reading, as above pointed out, is increased by two percent in order to take care of the volume of space occupied by the gas now under 50 atmospheres of pressure. By dividingthe gas space Volume thus obtained by the volume of the sample. and multiplying by one hundred the percent gas space per unitvol ume is obtained.

Also by noting the length of time required for the mercury to enter the pores a measure of the permeability is obtained. This procedure may be carried out rapidly'and a large number of .samples may be thus analysed in a short period of time.

With regard to the permeability, I have found that working with a sample of from one to four cubic inches, if more than 95% of the mercury enters the pores at 50 atmospheres in less than one second, the sand is sufiiciently permeable for oil production As various embodiments might be made of this invention, and as various changes might be made in the construction herein described, all without departing from the scope of the invention, it

is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

Iclaim:

1. In the art of measuring in a porous body the space filled with gas, the method comprising determiningthe volume of a'sample of the body by immersing it in liquid, forcing theliquid under pressure into the pores of said body to com-- press the gas in said pores and to occupy the space occupied by the gas, and measuring the liquid while under pressure necessary thus to supplant the gas.

2. The method of measuring the amount of free gas in the pores of a porous body, com.- prising immersing the body in a liquid whose surface tension and chemical properties are such that it does not of itself enter the pore'spaces, to determine the volume of the body, causing the liquid to enter the pore space to supplant the gas, and measuring the amount of liquid thus required while under pressure.

3. The method of measuring in a porous body the pore space filled by gas, comprising, coating the body with a substance to render it impervious to liquids, immersing the body thus coated in iiquid to measure the volume of the body,

causing the liquid to penetrate the coating and,

'to supplant the gas, and measuring the volume of the liquid thus needed.

4. The method of measuring in a porous body the pore space filled by gas, comprising, coating a sample of the body with a substance to render it impervious to liquids, immersing the sample thus coated in a body of liquid to measure the volume of the sample, subjecting to pressure the liquid in which the sample is immersed to cause it to penetrate the coating and to supplant the gas in the pore space, and measuring the amount of liquid required thus to fill the pore space.

5. The method of determining in a porous body the pore space occupied by gas, comprising the stepsof, immersing the body in mercury to determine the volume of the body, forcing the mercury under pressure into the pore space to compress and supplant the gas while the body is still immersed in the mercury, and measuring the amount of mercury while under pressure needed to supplant the gas.

6. The method of simultaneously measuring the permeability of a porous body whose pores are at least partially filled with gas, and messuring the percentage of free gas in the body, comprising, immersing. the body in a liquid to ,obtain the volume of the body, subjecting the liquid to a substantially constant elevated pres--- sure to cause it to enter the pores and compress the gas therein, measuring the time required for the liquid thus to supplant the gas, and measurlng the amount or liquid required to supplant the gas.

7. In apparatus for measuring the free gas content of a porous body, in combination, a sample chamber having a removable top conically recessed on its inside surface and provided with an outlet at the apex of the conical surface,

. thereof, a needle valve adapted to be moved into closing or opening positions. an inlet at thebottom of said chamber, a mercury pump adapted to force mercury into said chamber through said inlet to force mercury into the pores of a sample in said chamber, and means for measuring the amount of mercury thus forced into the pores of said sample.

9. The method ofmeasuring the permeability of a non-compressible porous body, the pores of which are at least partially filled with a gas, comprising immersing the body in a liquid. subjecting the liquid to a substantially constant elevated pressure to cause it to enter the pores and displace gas by compressing it therein, and noting the amount of liquid which thus enters and the time required for such entrance as an indication of the permeability of said body.

10. The method oi measuring thep rmeability or a non-compressible porous body. the pores of which are at least partially filled with a gas, comprlsingimmersingthebodyin aliquidwhose surface tension and chemical properties are such that it does not'of itself enter the pore spaces, subjecting the liquid to a substantially constant elevated pressure to cause it-to enter the pores and displace gas by compressingdt therein, and noting the amount of liquid which thus enters and the time required for such entrance as an indication of the permeability of said body.

11. The method of measuring the permeability of a non-compressible porous body, the pores of which are at least partially filled with a. gas, comprising coating the body with a substance to render it impervious to liquids, immersing the v bodyvin a liquid, subjecting the liquid to a substantially constant elevated pressure to cause it to penetrate the coating and enter the pores and displace gas by compressing it therein, and noting the amount of liquid which thus enters and the time required for such entrance as an indication of, the permeability of said body.

12. The method of measuring the permeability of a non-compressible porous body, the. pores of which are at least partially filled with a gas, comprising immersing the body in mercury, subjecting the mercury to a substantially constant elevated pressure to cause it to enter the pores and displace gas by compressing it therein, and noting the amount of mercury which thus enters and the time required for such entrance as an content or a porous body, in combination, a 

